Medication Injection Device with Automatic Needle Retraction Following Injection

ABSTRACT

An automatic medication injection device including a driver (95), a retractor (190, 230) and a blocking member (180). Upon device triggering the driver is shifted proximally to move a device syringe, expel medication from the syringe0, and then to disengage itself from the syringe plunger. The driver and the blocking member have a complementary camming configuration by which the blocking member, during the driver shifting, is automatically rotated from a first rotational orientation to a second rotational orientation. The blocking member blocks retraction of the retractor when disposed in the first rotational orientation, and permits retraction of the retractor when disposed in the second rotational orientation, which retractor retraction withdraws the device syringe from an injecting position to a retracted position.

BACKGROUND OF THE INVENTION

The present invention pertains to pharmaceutical injection devices, and,in particular, to an automatic medication injection device thatautomatically retracts a needle after an injection.

Patients suffering from a number of different diseases frequently mustinject themselves with pharmaceuticals. A variety of devices have beenproposed to facilitate these injections. One type of device is anautomatic medication injection device. This type of device typicallyincludes a trigger assembly that when operated by a user causes thedevice to automatically insert into the user a needle of a syringe thatprior to triggering was disposed within the device housing, and then thedevice automatically injects a dose of medication through that insertedneedle.

While perhaps useful, some automatic medication injection devices dosuffer from one or more shortcomings. For example, some known automaticmedication injection devices require a user to pull the device away froman injection site in order to withdraw the needle from the skin after aninjection. Such devices, whether the needle withdrawal be completelymanual or be spring-powered when triggered by a user starting to pullthe device away from an injection site, may be found undesirable to useby some people.

Some automatic medication injection devices may insert a needle orinject at speeds which have variability during the course of the deviceuse which do not promote an appropriate experience for some users. Inaddition, some automatic medication injection devices are bulky so as tomake the device less convenient to use inconspicuously.

Thus, it would be desirable to provide an automatic medication injectiondevice that can overcome one or more of these and other shortcomings ofthe prior art.

BRIEF SUMMARY

In one form thereof, the present invention provides an automaticmedication injection device including: a housing; a syringe filled withmedication and including a needle and a plunger; a driver shiftableproximally in the housing along a track from a ready position to aplunged position, the driver and the track and the plunger beingcomplementarily configured for the driver, when shifted from the readyposition to the plunged position, to advance the plunger to move thesyringe proximally from a start position, at which the needle isdisposed within the housing, to an injecting position, at which theneedle projects external to the housing, and to advance the plunger toexpel medication from the syringe through the needle, and to disengagefrom the plunger to permit axial movement of the driver relative to theplunger; a retractor having an opening in which the syringe extends, theretractor shiftable distally within the housing from a ready position toa retraction position to withdraw the syringe from the injectingposition to a retracted position at which the needle is disposed withinthe housing; a blocking member having an opening in which the syringeextends, the blocking member rotatable within the housing from a firstrotational orientation to a second rotational orientation, the blockingmember complementarily configured with the retractor to block movementof the retractor from the ready position to the retraction position whendisposed in the first rotational orientation, and to permit movement ofthe retractor from the ready position to the retraction position whendisposed in the second rotational orientation; at least one biasingmember preloaded to urge the driver proximally and to urge theretraction member distally; a trigger actuatable to allow the at leastone biasing member to move the driver from the ready position to theplunged position; and the driver and the blocking member having acomplementary camming configuration for the blocking member to beforcibly rotated automatically from the first rotational orientation tothe second rotational orientation when the driver shifts from the readyposition to the plunged position.

One advantage of the present invention is that an automatic medicationinjection device may be provided which provides for needle insertion,injection, and then retraction during use in an automatic manner withoutuser intervention after an initial device triggering.

Another advantage of the present invention is that an automaticmedication injection device may be provided which is easy to handle anduse.

Another advantage of the present invention is that an automaticmedication injection device may be provided which can insert a needleand/or inject through a needle at one or more relatively constantspeeds.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other advantages and objects of this invention,and the manner of attaining them, will become more apparent, and theinvention itself will be better understood, by reference to thefollowing description of embodiments of the invention taken inconjunction with the accompanying drawings, wherein:

FIG. 1 is a front view of an automatic medication injection device,which device is shown in a locked arrangement prior to use;

FIG. 2 is a front view of the automatic medication injection device ofFIG. 1 with both the needle shield and the front half of the housingremoved, and after the device has been shifted from the lockedarrangement to an unlocked or ready arrangement;

FIG. 3 is an exploded perspective view of the automatic medicationinjection device of FIG. 1, where the needle shield is not shown;

FIGS. 4a, 4b, 4c, 4d, 4e and 4f are respectively perspective, front,back, side, top and bottom views of a shell half of the housing upperportion shown separate from the other device components;

FIGS. 5a, 5b, 5c, 5d, 5e and 5f are respectively perspective, front,back, side, top and bottom views of a shell half of the housing lowerportion shown separate from the other device components;

FIGS. 6a, 6b, 6c, 6d, 6e and 6f are respectively perspective, bottomperspective, front, side, top and bottom views of a button shownseparate from the other device components;

FIG. 7 is a partial view of a housing upper portion showing its buttontrack in a two-dimensional form;

FIGS. 8a, 8b, 8c, 8d and 8e are respectively perspective, front, side,top and bottom views of one piece of a biased drive element assemblyshown separate from the other device components;

FIGS. 9a, 9b, 9c, 9d and 9e are respectively perspective, front, side,top and bottom views of a second piece of a biased drive elementassembly shown separate from the other device components;

FIGS. 10a, 10b, 10c and 10d are respectively perspective, side, top andbottom views of a plunger rod shown separate from the other devicecomponents;

FIGS. 11a, 11b and 11c are respectively a bottom perspective, front andtop views of a syringe clip shown separate from the other devicecomponents;

FIGS. 12a, 12b, 12c, 12d and 12e are respectively perspective, side,front in longitudinal cross-section, top and bottom views of a syringeguide shown separate from the other device components;

FIGS. 13a, 13b, 13c, 13d and 13e are respectively perspective, front,side, top and bottom views of an upper spring retainer shown separatefrom the other device components;

FIGS. 14a, 14b, 14c and 14d are respectively perspective, front, sideand top, as well as bottom, views of a lower spring retainer shownseparate from the other device components;

FIGS. 15a, 15b, 15c, 15d, 15e and 15f are respectively perspective,front, side, top, bottom and bottom perspective views of a retractionplate shown separate from the other device components;

FIG. 16 is a front view similar to the view of FIG. 2 after themedication in the device has been delivered and immediately prior toneedle retraction; and

FIG. 17 is a front view similar to the view of FIG. 16 after needleretraction.

Corresponding reference characters indicate corresponding partsthroughout the several views. Although the drawings represent anembodiment of the present invention, the drawings are not necessarily toscale, and certain features may be exaggerated or omitted in some of thedrawings in order to better illustrate and explain the presentinvention.

DETAILED DESCRIPTION

Referring now to FIGS. 1 and 2, there are shown two views of anautomatic medication injection device, generally designated 20. When thetrigger assembly of device 20 is operated, the needled syringe of thedevice 20 is automatically driven downward such that its injectionneedle projects beyond the bottom end 27 of the device housing topenetrate the user. The device then proceeds to inject automatically,that is without further user action, the medication contents of thesyringe through the needle, after which the syringe is retractedautomatically such that the needle is returned to within the housing.

Device 20 includes an outer housing 22 in which are operationallydisposed working components of the device. The outer housing 22 isformed by an upper portion 24 and a lower portion 26. The housing upperportion 24 is formed by two identical, mating shell halves 28, 28′ thatare fixedly secured together. The housing lower portion 26 is alsoformed by two identical, mating shell halves 30, 30′ that are fixedlysecured together. The housing upper portion 24 and housing lower portion26 are also fixedly secured to each other. Suitable manners ofsecurement are known, such as adhesives with the aid of interfittingpins and holes. Different housing shapes and manufacturing assembliesmay naturally be used, such as making the upper portion integral withthe lower portion, but with mating halves or parts.

A button 35 that is part of the trigger assembly protrudes in the axialdirection from the top or distal end of housing portion 24. As usedherein, distal and proximal refer to axial locations relative to aninjection site when the device is oriented for use at such site,whereby, for example, proximal end of the housing refers to the housingend 27 that is closest to such injection site.

Button 35 is molded as a single piece from a suitably durable plasticmaterial. As further shown in FIGS. 6a -6 f, button 35 includes an enddisc 40 with a skirt 42 extending proximally from the outer periphery ofdisc 40. End disc 40 has a concave face 44 upon which a force can bedirectly applied in a comfortable fashion by a user to selectivelyplunge button 35 to trigger the device.

Two flexible wall sections 46 spaced one hundred eighty degrees apartaround skirt circumference are defined by vertically extending slots 48formed at the proximal end 49 of skirt 42. A pin 50 extends radiallyoutward from and is formed integrally with each wall section 46. Pins 50serve as followers that fit into and can slide within tracks 52 providedin housing halves 28, 28′ near housing distal end 33. Two pins 50 spaced180 degrees apart around the button periphery are provided to balanceforces and to provide a robust design, but fewer or additional pins andassociated housing tracks may be provided.

Tracks 52 are shown as openings extending through housing halves 28, 28′but alternatively could be recesses formed on the inner walls of suchhalves. In a still alternate embodiment, rather than being directlyprovided on the outer housing, tracks 52 could be provided on componentsthat are secured to housing 22. The arrangement of the tracks 52 andfollowers 50 on the housing halves and the button could be switched. Theflexibility of wall sections 46 resulting from slots 48 aids in assemblyof the button 35 with the outer housing 22.

The inner surface 57 of skirt 42 defines an interior hollow 55 in whicha drive element 60 of the trigger extends. Although shown as beingcontinuous but for the slots 48, skirt 42 need not be so configured,such as by including openings therein, while still providing an interiorhollow in which the drive element may be provided.

The trigger drive element 60 is shown as a single plate-shaped memberwithin interior hollow 55 which extends downward from disc 40 anddivides the interior hollow 55 in half. Plate 60 is transverselyoriented relative to the axial direction in which skirt 42 extends, andarranged diametrically within the cylindrical hollow 55. Althoughcontinuous in its transverse spanning of hollow 55 in the shownembodiment, in alternate embodiments the trigger drive element may bediscontinuous, such as if it were provided as two smaller flanges, orcantilevered from one region of the inner circumference of skirt 42, orif it depended from the underside of button disc 40 in spacedrelationship with skirt inner surface 57.

A biasing element 63 provides a biasing force urging button 35 upwardrelative to outer housing 22. Biasing element 63 is shown in FIG. 2 as apreloaded coiled spring having an upper end 64 that engages the buttonproximal end 49 and a lower end 65 that seats on radially protrudingribs 67 provided on the inner walls of housing halves 28, 28′. Differentknown types of biasing elements could alternatively be used.

Movement of button 35 relative to housing 22 is guided by theconfiguration of tracks 52 in which pins 50 travel. With additionalreference to FIG. 7, each track 52 defines an unlocking travel path 66,a triggering travel path 68, and a button retracting path 70. Whenbutton 35 is in a locked arrangement because pins 50 are at lockedpositions 72, any attempt by a user to plunge button 35 downward or intohousing 22 to trigger an injection is thwarted by the abutment of pins50 against the housing edge 69 that defines the lower extent of path 66.Unlocking travel path 66 starts at an angular end or locked position 72and extends horizontally or circumferentially at 74 until reaching anangled upward branch 76 having an upper end 77 that serves as anunlocked or ready position

The triggering travel path 68 begins at a position 80 directly belowupward branch 76. Travel path 68 continues from position 80 to an axialdownward and angularly offset position 82. The housing edge 84 thatdefines the lower extent of path 68 between positions 80 and 82 servesto cam pins 50 to thereby rotate button 35 within housing 22 as button35 is plunged downward. Edge 84 can serve its camming function whilebeing straight as shown or by being differently shaped, such as strictlyarcuate. The upper edge 85 defining the upper extent of path 68 forms alobe 87 that does not impact button plunging but which serves as anabutment that guides pins 50, with the assistance of biasing element 63,into upward branches 76 during device unlocking.

Button retracting path 70 continues from position 82 to an upward andangularly offset position 86. The upper edge 90 defining the upperextent of path 70 is shaped to urge a pin 50 that is pushed by the forceof spring 63 upward against it to move toward position 86, therebypromoting a proper rotation of button 35.

During the triggering of device 20, the trigger drive element 60operatively engages at least one upstanding member that extends from adrive element that is biased down by a biasing element other than spring63. The biased drive element of device 20 is for the shown embodimentidentified generally at 95 and is assembled from a first piece 96 and asecond piece 100 that are fixedly secured together during manufacture.Biased drive element 95 serves as a driver of a plunger in the shownembodiment.

The foregoing as well as subsequent description of the assembly used totrigger operation of device 20 is provided for purposes of illustrationand is not intended to limit a device of the present invention to such atrigger. Instead, alternate triggers, such as one or more latchingprongs that are cammed out of a latching engagement by a strictlyaxially moving button, or others that have a known form, may beemployed. The shown trigger mechanism may be further understood in viewof a provisional patent application, filed with the United States Patentand Trademark Office on the same date of this application and entitled“Trigger Assembly for Automatic Medication Injection Device”, the entiredisclosure of which application is incorporated herein by reference.

Biased drive element piece 96 is further shown in FIGS. 8a-8f andincludes an axially extending body 102 through which an axiallyextending, cylindrical opening or throughbore 104 is provided. Aroundits periphery the body 102 includes two curved body sections 105 and 106that are each provided with a follower in the form of a pin 108. Bodysections 105 and 106 are circumferentially spanned by flat body sections110 and 112 each provided with a mounting pin 114. Pins 108 slide withintracks generally designated 109 provided in housing halves 28, 28′.Although shown as openings extending through housing halves 28, 28′,tracks 109 could be differently provided, such as recesses formed on theinner walls of the housing halves, or on components that are secured tohousing 22.

As further shown in FIG. 4c , each track 109 sequentially includes ahorizontally aligned release region 310, an axially or verticallyaligned driving region 312 that begins at one angular end 314 of releaseregion 310, and an angled region 316 that beings at the bottom end 318of driving region 312, and extends back in the angular direction towardrelease region 310 to an end 320 generally below the start end 322 ofrelease region 310. Fewer or additional pins 108 and tracks 109 thanshown may be used. At the distal end 115 of body 102, opening 104 isradially enlarged so that a substantially annular seat 116 is formed. Atthe proximal end 120 of body 102, each body section 105 and 106 isprovided with a depending flange 122 having an angled end 124 forcamming purposes described below, which angling extends in thecircumferential direction.

Biased drive element piece 100 is further shown in FIGS. 9a-9f andincludes a generally disc-shaped body 128 with a keyed opening 133centrally provided therethrough. Body 128 is sized and shaped to fit inthe top of body 102 so as to seat on annular seat 116, wherein it isfixedly secured such as with adhesives so that biased drive elementspieces 96 and 100 function as a single part.

Biased drive element piece 100 includes a trigger componentcomplementarily designed with the trigger drive element 60 of button 35.This complementary design achieves a transfer of rotational motion tothe biased drive element piece 100 during button plunging, andpreferably does not cause the biased drive element piece 100 to movewhen the button, if provided with such functionality as in the shownembodiment, is rotated to be unlocked.

At least one, and in the shown embodiment a pair of, upstanding members130 which are part of the device trigger mechanism project upward fromthe top surface 129 of body 128. Each upstanding member 130 isbar-shaped with a slight curving as it extends in the angular direction.Members 130 are disposed on opposite sides of body opening 133, and arein spaced relationship in the horizontal direction to provide an openingor gap 134 therebetween in which fits trigger drive element 60 whendevice 20 is assembled. The size and spacing of members 130 iscomplementarily shaped with drive element 60 so that a rotation ofbutton 35 when plunged such that its pins 50 move from position 80 toposition 82 forces a rotation of the biased drive element 95. In analternate embodiment, and provided accommodations were made for thekeyed opening 133 and its function, the upstanding members 130 could bereplaced with an upstanding, off-centered flange equivalent to driveelement 60, and the drive element 60 could be replaced with dependingmembers equivalent to members 130. Still further, the upstanding membersalternatively may be differently shaped.

The biased drive element 95 acts on a plunger rod, generally designated140, when shifted proximally in the device housing from a ready positionimmediately prior to moving axially to a plunged position after suchaxial movement. As further shown in FIGS. 10a -10 d, plunger rod 140 ismolded to include an upper bar 142 that extends from a disc portion 144.Upper bar 142 has along the majority of its height a periphery sized andshaped to be able to closely fit within keyed opening 133. Thisperiphery is different at the upper region 145 of upper bar 142 due toopposite corners 147 and 148 being beveled to form axially upwardlyfacing ledges 152. A cruciform shaped lower bar 155 sized and shaped tofit within a medication syringe depends from disc portion 144. The endregion 157 of lower bar 155 is radially enlarged and includes a proximalend face 158 that operationally abuts syringe piston 167 during plungeradvancement. The radial enlargement of end region 157 may help ensurethe plunger rod stays secure within the syringe 160. Plunger rod 140 maybe formed of two or more pieces fixedly secured together, such as withset screws, or may be formed as a single piece.

As further shown in FIG. 3, device 20 includes a medication-filledsyringe of conventional design. The syringe, generally designated 160,includes a barrel 162 with a flange 164 at its distal end, and aninjection needle 166 mounted at the proximal end of barrel 162 and influid communication with the medication contents of the barrel. Syringepiston 167 seals with the interior wall of barrel 162 and is sealinglyadvanceable to force the medication within the barrel out the needle166. Syringe piston 167 and plunger rod 140 together serve in the shownembodiment as a plunger of the syringe of device 20. In an alternateembodiment, the plunger and driver of the device that work together toachieve the operational functionality may be differently formed.

A syringe clip 170 further shown in FIGS. 11a-11c includes atransversely opening, syringe flange-accommodating hollow 172 and mountsto syringe barrel flange 164 to be rotatably fixed together. The syringeclip 170 can frictionally lock to flange 164, possibly with the aid ofan inner lining having a high coefficient of friction, or can with amodification in the syringe flange and clip design have a keyed togetherfit. The top wall 175 of clip 170 includes a keyed opening 177 whichmatches the size and shape of and receives plunger rod bar 155 to limitthe rotation of plunger rod 140 relative to syringe barrel 162. Syringeclip 170 aids in locating the syringe 160 within the interior of thedevice housing.

In an alternate embodiment, the lower bar 155 may have a different shapethan the cross shape shown, for example a D-shape cross-section, thatfits with a corresponding keyed opening in a modified syringe clip 170.Also, the syringe clip could be still differently shaped than asdescribed above, such as a plate that is fixedly secured to the syringeflange, such as with set screws, and without a transversely openinghollow for the flange.

Syringe barrel 162 freely extends through an opening or throughhole 182in retraction plate 180 and an opening or throughbore 192 in an upperspring retainer 190. The proximal region of barrel 162 fits within anopening or bore 202 through a body 204 of syringe guide 200, which guideis further shown in FIGS. 12a -12 e. Body 204 is generally annular andextends from a distal face 208 to a proximal face 207. Bore 202 has areduced diameter portion 203 at its proximal end which allows passagetherethrough of the needle 166 and reduced diameter needle-holding end168 of the syringe barrel. The region of body 204 that defines boreportion 203 provides an annular collar 206 shaped to correspond to thebarrel neck and to prevent passage of the syringe barrel 162 entirelythrough the syringe guide 200. Guide body 204 is sized to have africtional fit with barrel 162 that resists rotational motion of thesyringe 160 within syringe guide 200.

Each of throughhole 182, throughbore 192, bore 202 and bore 232 arecircumscribed by the bodies of the elements in which they are providedin the shown embodiment. In alternate embodiments, one or more such holeor bores may be not so completely ringed or circumscribed so long as thefunctionality of such element is not compromised. Throughhole 182,throughbore 192, bore 202 and bore 232 are all coaxially aligned withkeyed opening 133 as well as the longitudinal axis of syringe 160.

Syringe guide 200 is rotatably fixed and axially shiftable relative toan upper spring retainer 190 that is further shown in FIGS. 13a -13 e.This relationship is provided by flange-shape keys 210 of syringe guide200 which are slidable within axially extending slots 215 in body 214 ofupper spring retainer 190 when guide 200 shifts within a radiallyenlarged portion 193 of throughbore 192. Syringe guide 200 may provide africtional fit with retainer 190 to hold the syringe 160 in a retractedposition.

In an alternate embodiment not shown, syringe 160 can be held in aretracted position by the combination of syringe clip 170 seating on theupper extent of end region 157, and the plunger rod 140 releasablycatching on biased drive element piece 100, such as via one or more pinsat the top end of plunger rod 140 that engage top surface 129 until suchpins are aligned to fit through opening 133 after biased drive elementpiece 100 is rotated during triggering.

Two spacing fingers 220 project upward in the axial direction from theupper face 221 of body 214. The distal faces 222 of fingers 220 engageretracting plate 180 as described below. Fingers 220 are disposed ondiametrically opposed sides of throughbore 192.

An annular assembly collar 224 depends from the proximal end of body214. The hollow interior 225 of collar 224 allows for the injectionneedle 166 to extend therethrough. Slots 226 aligned with slots 215allow for insertion of syringe guide 200 into body 214 during deviceassembly. Collar 224 fits within a central, cylindrical bore or aperture232 axially extending through lower spring retainer 230. Collar 224 isfixedly secured within bore 232, such as by adhesively attaching, and/orattaching using screws or other fasteners, collar 224 to retainersurface 234.

As further shown in FIGS. 14a -14 d, lower spring retainer 230 includesgrooves or keyways 236 on opposite sides of its body 238. Keyways 236fit over vertically extending ribs or keys 240 in the interior hollow242 of each of shell halves 30, 30′ of housing lower portion 26, andlower spring retainer 230 is sized to be slideable in the axialdirection within hollow 242. With reference to shell half 30′ shown inFIGS. 5a -5 f, each of shell halves 30 and 30′ include a semi-circularnotch 245 in an upper wall 246 and a semi-circular notch 248 in a lowerwall 249. In the assembled device 20, the notches 245 define a circularopening sized and shaped to freely receive spring retainer body 214 andbiasing springs described further below, while notches 248 define asmaller circular opening sized to merely allow passage of the needle 166and fitting of the needle shield 29 over needle 166 before device use.

In the shown embodiment, lower spring retainer 230 and upper springretainer 190 serve with syringe guide 200 as a retractor of the syringeafter an injection. The retractor is shiftable distally to withdraw thesyringe from an injection position to a retracted position at which thesyringe needle is disposed within the housing.

Lower spring retainer 230 is connected to the proximal end of biasingsprings used to power the medication delivery by device 20. Biasingsprings of device 20 are shown in FIG. 3 as a pair of constant forcesprings 260 made of a thin slat of metal that have their proximal endswound at 261 around pins 262. The ends of pins 262 fit within transversebores 264 formed in facing body arms 268. Each pin 262 spans, with itswound spring portion 261 fitting within, a notch 270 in body 238 thatdefines facing body arms 268.

Springs 260 are connected with the biased drive element that drives thesyringe motion by extenders 275 that are made of metal or other suitablyrobust material. A boss 277 provided near the proximal end of eachextender 275 snap fits within a hole 279 provided near the distal end280 of a spring 260. Each extender 275 also includes a hole 283 near itsdistal end that receives a pin 114 of biased drive element piece 95.Extenders 275 facilitate biased drive element 95 turning relative to thesprings 260 during device operation. Springs 260 alternatively may beconnected directly to pins 114 using holes 279.

Spring 260 are shown as two in number disposed on opposite sides of thespring retainer formed by the assembly of upper spring retainer 190 andlower spring retainer 230. Such a spring configuration provides abalancing of forces within the device, but fewer or additional springscould be employed. Each spring 260 is preloaded and shown to haveconstant force properties to cause a constant force to be provided toshift the syringe downward so as to insert the needle 166 into a user, aconstant force to be provided to force the medication contents of thesyringe 160 through the needle 166, and a constant force to retract theneedle 166 into the housing 22 after dose delivery. In addition, in analternate embodiment, such as by having different sections of thesprings 260 having different widths, springs 260 can provide oneconstant force during one phase of operation and a different constantforce during another phase of operation. Springs that do not provideconstant force during one or more or all phases of device operation mayalternatively be employed.

In alternate embodiments, one or more additional springs, as well aspossibly different configurations of springs 260, may be employed toprovide benefit to device operation. For example, one or more additionalsprings may be interposed, in a preloaded state, between the bottomsurface of lower spring retainer 230 and the lower wall 249 of shellhalves 30, 30′ of housing lower portion 26, which interposed springsprovide a force to assist springs 260 in retracting the syringe needlewithin the housing after an injection. Furthermore, such interposedsprings could provide the sole syringe retraction force, such as ifsprings 260, at their lower ends, were not operatively attached to thelower spring retainer but instead were attached directly to the housing,such as interior walls of housing lower portion 26 if lower springretainer 230 were made smaller to allow such spring positioning.

A retraction plate 180 further shown in FIGS. 15a-15f is used to stageneedle retraction by serving as a blocking member. Ribs or keys 290 thatprotrude radially outward fit within horizontal grooves 292 in housingshell halves 28, 28′ and slide therein so that retraction plate 180 isaxially captured but rotatably shiftable within outer housing 22. Theunderside 294 of plate 180 includes two notches 295 that open to theoblong throughhole 182 and provide two axially facing stop surfaces 297.When retraction plate 180 is in a blocking rotational position withinhousing 22 associated with device 20 being in a pre-injectionarrangement, the spacing fingers 220 of upper spring retainer 190project within notches 295 so that finger distal faces 222 abut stopsurfaces 297. When retraction plate 180 is in a second rotationalposition within housing 22 for needle retraction, fingers 220 projectwithin throughhole 182 to be freely insertable therethrough.

The top surface 300 of retraction plate 180 includes two bosses 302 onopposite sides of throughhole 182. Each boss 302 has an angular end 304that serves as a push surface during the forced rotation of theretraction plate 180. The cut out that creates surfaces 306 and 308serves as an opening through which springs 260 axially extend, as wellas reduces points of contact with the housing, which contacts pointswould otherwise create additional frictional resistance to rotation.

Retraction plate 180 could also be modified in a not shown alternateembodiment to provide a more robust design that also serves a guidingfunction. For example, the periphery of plate 180, at opposite regionsof its circumference, could include downwardly depending flanges. Theseflanges would generally flank upper spring retainer 190 and guide thatretainer 190 as it moves upward to have fingers 220 insert withinthroughhole 182 as described below. The flanges may be designed toassist fingers 220 by engaging upper spring retainer 190 to prevent theretainer 190 from moving upward when the retraction plate 180 is in afirst or starting rotational position within the housing, and by beingfree of the retainer 190 to allow upward motion of retainer 190 into thespace between the flanges when the retraction plate 180 reaches itssecond rotational position. In addition, in this alternate embodimentthe bottom ends of the downwardly depending flanges could serve as stopsagainst which shoulders of the upper spring retainer 190 abut to haltthe syringe retraction after use at a desired height.

The construction of device 20 will be further understood in view of adescription of its operation. A user starts with a device 20 configuredin a locked state as supplied by the manufacturer and as shown in FIG.1.

A user first pulls the needle shield 29 off the device. The needle 166of syringe 160 does not extend at this point beyond the base of housinglower portion 26 and is still protectively housed within housing 22.

To unlock the device 20 for injection, button 35 is manually rotatedrelative to housing 22 such that pins 50 slide along travel paths 66until reaching ends 77. Spring 63 urges the button 35 upward toencourage the pins 50 to travel toward ends 77. During this buttonrotation, neither the biased drive element 95 nor any of the otherinternal components are moving, and notably trigger drive element 60spins within gap 134 without movably contacting upstanding members 130.At this point the device 20 is arranged as shown in FIG. 2.

To begin an injection when device 20 is properly positioned on aninjection site, when a user subsequently applies a manual plunging forceon face 44 of button 35 sufficient to overcome spring 63, button 35first moves downward and pins 50 slide past lobe 87 and reach position80. Further button plunging by the user from that point causes button 35to rotate as pins 50 slide along the angled housing edge 84 untilreaching the position 82. The button rotation within housing 22resulting from pins 50 moving from position 80 to position 82 forcesbiased drive element 95 to turn within housing 22 due to trigger driveelement 60 drivingly contacting members 130. During this turning ofbiased drive element 95, pins 108 slide within track release regions 310until reaching ends 314. This rotation of biased drive element 95 doesnot move plunger rod 140, despite the distal end 149 being at this pointdisposed at an elevation above or within the keyed opening 133 of biaseddrive element body 128. Rather, during this rotation, the biased driveelement 95 moves such that portions of the surface that forms its keyedopening 133 end up adjacent to the surfaces of beveled corners 147, 148.Removal of a plunging force on button 35 at any time after pins 50 reachposition 82 results in the button 35 being urged up by spring 63 tocause the button to move up and rotate till pins 50 reach position 86.

When pins 108 reach track end 314 in alignment with track driving region312, biased drive element 95 is driven or pulled downward, with pins 108traveling down track driving region 312, due to a downward pulling forceof constant strength on biased drive element 95 resulting from apreloading of springs 260 during manufacturing assembly. The assembly oflower spring retainer 230 and upper spring retainer 190 is not pulled upwithin the housing 22 at this time by this spring preloading due to theabutment of fingers 220 with retraction plate 180.

As biased drive element 95 moves downward, keyed opening 133 first movesdown around plunger upper region 145 without moving plunger rod 140.When biased drive element 95 moves down sufficiently, the underside 131of body 128 abuts ledges 152, and continued downward motion of biaseddrive element 95 powered by springs 260 drives plunger rod 140 down.This downward driving of plunger rod 140 pushes the syringe piston 167proximally, which motion first shifts syringe barrel 162 proximallyrelative to the outer housing 22, with guide 200 sliding within slots215. Motion of syringe barrel 162 proximally is halted when guide keys210 abut top surface 239 of lower spring retainer 230, at which pointthe tip of needle 166 projects beyond the housing proximal end 27 forpenetrating a user's skin. Continued downward driving of plunger rod 140by biased drive element 95 powered by springs 260 pushes syringe piston167 to slide within the syringe barrel 162 to force the medicationcontents of the syringe through that needle 166 for an injection.

Throughout the needle insertion and the start of the medicationinjection process described above, pins 108 are traveling down trackdriving region 312 with biased drive element 95 translating withoutrotation within housing 22. When pins 108 reach end 318 of track drivingregion 312, the medication contents are not yet completely delivered,and pins 108 continue into and slide downward within angled region 316of track 109. Biased drive element 95 translates as well as rotateswithin housing 22 when pins 108 slide along angled region 316. Due tothe keying of plunger rod 140 to syringe clip 170, and the amount ofresistance to rotation provided between syringe clip 170 and syringe 160as well as between syringe 160 and syringe guide 200, as biased driveelement 95 so rotates, the underside 131 of body 128 begins to spin onthe ledges 152 as it continues to drive the plunger rod 140 proximally.When biased drive element 95 has rotated sufficiently, which point isdesigned to correspond to when the syringe piston 167 has forced aproper dose from the syringe 160 and pins 108 have reached end 320 ofangled region 316 so that movement of biased drive element 95 isstopped, keyed opening 133 clears ledges 152. This ledge clearance willallow retraction of the plunger rod 140.

When biased drive element 95 so rotates within housing 22 when pins 108slide along angled region 316 as described above, it has a camming,driving relationship with retraction plate 180. The angled ends 124 offlanges 122 contact angular ends 304 of bosses 302, and the rotation ofbiased drive element 95 drives the rotation of retraction plate 180within housing 22. When pins 108 reach ends 320 of track angled regions316, retraction plate 180 reaches a point of sufficient rotation atwhich stop surfaces 297 are angularly clear of finger distal faces 222,thereby allowing fingers 220 to insert within retraction plate opening182. The clearance of ledges 152 by keyed opening 133 is designed to besimultaneous with retraction plate surfaces 297 being clear from fingerdistal faces 222. FIG. 16 shows device 20 arranged at this point ofoperation.

When fingers 220 are aligned to insert within opening 182, springs 260pull the assembly of lower spring retainer 230 and upper spring retainer190 upward within housing 22 until top surface 239 of lower springretainer 230 abuts the inside of the upper wall 246 of housing lowerportion 26. Because syringe guide keys 210 are abutting surface 239, theupward pulling of the assembly of lower spring retainer 230 and upperspring retainer 190 lifts the syringe 160 within housing 22 to retractthe tip of needle 166 into a protectively housed position within housing22. As the syringe 160 is being so retracted, plunger rod 142 extendsfurther upward through keyed opening 133. At this point, device 20 hascompleted its operation and is arranged as shown in FIG. 17.

While this invention has been shown and described as multiple possibledesigns, the present invention may be modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains.

We claim:
 1. An automatic medication injection device comprising: ahousing; a syringe filled with medication and including a needle and aplunger; a driver shiftable proximally in said housing along a trackfrom a ready position to a plunged position, said driver and said trackand said plunger being complementarily configured for said driver, whenshifted from said ready position to said plunged position, to advancesaid plunger to move said syringe proximally from a start position, atwhich said needle is disposed within said housing, to an injectingposition, at which said needle projects external to said housing, and toadvance the plunger to expel medication from the syringe through saidneedle, and to disengage from said plunger to permit axial movement ofsaid driver relative to said plunger; a retractor having an opening inwhich said syringe extends, said retractor shiftable distally withinsaid housing from a ready position to a retraction position to withdrawsaid syringe from said injecting position to a retracted position atwhich said needle is disposed within said housing; a blocking memberhaving an opening in which said syringe extends, said blocking memberrotatable within said housing from a first rotational orientation to asecond rotational orientation, said blocking member complementarilyconfigured with said retractor to block movement of said retractor fromsaid ready position to said retraction position when disposed in saidfirst rotational orientation, and to permit movement of said retractorfrom said ready position to said retraction position when disposed insaid second rotational orientation; at least one biasing memberpreloaded to urge said driver proximally and to urge said retractionmember distally; a trigger actuatable to allow said at least one biasingmember to move said driver from said ready position to said plungedposition; and said driver and said blocking member having acomplementary camming configuration for said blocking member to beforcibly rotated automatically from said first rotational orientation tosaid second rotational orientation when said driver shifts from saidready position to said plunged position.
 2. The automatic medicationinjection device of claim 1 wherein said blocking member comprises abody including one of a key and a groove, and an interior surface ofsaid housing comprises the other of said key and said groove, said keysliding within said groove when said blocking member rotates from saidfirst rotational orientation to said second rotational orientation. 3.The automatic medication injection device of claim 1 wherein saidblocking member comprises a body, and said opening in said blockingmember is circumscribed by said body.
 4. The automatic medicationinjection device of claim 1 wherein said retractor comprises a body, andsaid opening in said retractor is circumscribed by said body.
 5. Theautomatic medication injection device of claim 1 wherein said retractorincludes at least one finger that projects from a distally facingsurface of a body of said retractor and which terminates in a distalend, and wherein a body of said blocking member includes at least onenotching on an underside surface, said at least one notching extendingfrom said opening in said blocking member, wherein said distal end ofsaid at least one finger fits within said at least one notching whensaid blocking member is in said first rotational orientation and engagessaid body of said blocking member so that said retractor is blocked frommoving from said ready position to said retraction position, said atleast one finger fitting within said opening in said blocking memberwhen said blocking member is in said second rotational orientation. 6.The automatic medication injection device of claim 5 wherein said atleast one finger includes two fingers that are disposed on oppositesides of said opening in said retractor and extend in an axialdirection.
 7. The automatic medication injection device of claim 1wherein said at least one biasing member comprises a constant forcespring.
 8. The automatic medication injection device of claim 1 whereinsaid at least one biasing member has opposite ends operatively attachedto said driver and said retraction member.
 9. The automatic medicationinjection device of claim 8 wherein said at least one biasing membercomprises a constant force spring having a winding that encircles a pinmounted to said retractor.
 10. The automatic medication injection deviceof claim 1 wherein said a least one biasing member comprises a pair ofconstant force springs axially extending along opposite sides of saidretractor.
 11. The automatic medication injection device of claim 1wherein said track comprises an axially extending slot that opens to anangled slot, both said axially extending slot and said angled slot beingprovided on said housing, and wherein said driver includes a followerthat slides within said axially extending slot and said angled slot. 12.The automatic medication injection device of claim 1 wherein said driverincludes a keyed opening for engaging said plunger, and wherein saidkeyed opening and said retractor opening and said blocking memberopening are coaxially aligned with said syringe.
 13. The automaticmedication injection device of claim 1 wherein said driver includes akeyed opening for said plunger, and said plunger includes a ledge onwhich said driver applies a plunging force, said driver rotatablerelative to said plunger to disengage from said ledge to permit saidplunger to move axially through said keyed opening.
 14. The automaticmedication injection device of claim 1 further comprising a syringeguide in which non-rotatably fits said syringe, said syringe guide keyedwith said retractor to permit limited relative axial movement and toprevent relative rotational motion, said retractor driving said syringeguide distally to withdraw said syringe from said injecting position tosaid retracted position.